1. Field of the Invention
The present invention relates to a method for manufacturing a liquid crystal display (LCD) device, and more particularly, a working range setting method for a bonding device for manufacturing an LCD device.
2. Discussion of the Related Art
In response to an increasing demand for various types of display devices, liquid crystal display (LCD), plasma display panel (PDP), electro-luminescent display (ELD), and vacuum fluorescent display (VFD) have been developed. In particular, LCD devices are commonly used because of their high resolution, light weight, thin profile, and low power consumption. In addition, LCD devices have been implemented in mobile devices, such as monitors for notebook computers, and have been developed for monitors of computers and televisions. Accordingly, efforts to improve image quality of LCD devices contrast with the benefits of their high resolution, light weight, thin profile, and low power consumption. In order to incorporate LCD devices as a general image display, image quality such as fineness, brightness, large-sized area, for example, must be improved.
LCD devices are provided with an LCD panel for displaying image data and a driving unit for applying a driving signal to the LCD panel. The LCD panel is provided with first and second glass substrates bonded at a certain distance with liquid crystal material injected therebetween. A plurality of gate lines are formed along a first direction at fixed intervals on a first glass substrate (TFT array substrate), and a plurality of data lines are formed along a second direction perpendicular to the first direction, thereby defining a plurality of pixel regions. Then, a plurality of pixel electrodes are formed in a matrix arrangement at the pixel regions, and a plurality of thin film transistors (TFT) are formed at the pixel regions. Accordingly, the plurality of thin film transistors are enabled by signals transmitted along the gate lines and transfer signals transmitted along the data lines to each pixel electrode.
In order to prevent light leakage, black matrix films are commonly formed on a second glass substrate (color filter substrate) except at regions of the second glass substrate corresponding to the pixel regions of the first glass substrate. Also, a red, green, and blue color filter substrate is formed on the second glass substrate to generate colored light, and a common electrode is formed on the color filter substrate to produce images.
Processes for manufacturing LCD devices include injection and drop methods. The injection method, according to the related art, includes steps of forming a sealant pattern on one of the first and second substrates to form an injection inlet, bonding the first and second substrates to each other within a vacuum processing chamber, and injecting liquid crystal material through the injection inlet. The drop method according to the related art, which is disclosed in Japanese Patent Application Nos. 11-089612 and 11-172903,includes steps of dropping liquid crystal material on a first substrate, arranging a second substrate over the first substrate, and moving the first and second substrates to be adjacent to each other, thereby bonding the first and second substrates to each other.
However, the injection method required a considerably long process time since liquid crystal material is injected by osmotic pressure in a vacuum state. Accordingly, the injection method is inadequate for fabrication of large-sized LCD devices. On the other hand, the drop method is a considerably shorter process time since the liquid crystal material is deposited on a first substrate and then bonded with a second substrate.
FIG. 1 is a cross sectional view of a bonding device for a liquid crystal display device according to the related art prior to a bonding process. In FIG. 1, a substrate bonding device includes a frame 10, an upper stage 21, a lower stage 22, a sealant dispenser (not shown), a liquid crystal material dispenser 30, a processing chamber including an upper chamber unit 31 and a lower chamber unit 32, a chamber moving system 40, and a stage moving system 50. The chamber moving system 40 includes a driving motor driven to selectively move the lower chamber unit 32 to a location at which the bonding process is carried out, or to a location at which outflow of the sealant and dropping of the liquid crystal material occur. The stage moving system 50 includes another driving motor driven to selectively move the upper stage 21 along a vertical direction perpendicular to the upper and lower stages 21 and 22.
A receiver-stopper system temporarily supports a substrate 52, which is attached to the upper stage 21, at both diagonal positions of the substrate 52 when an interior of the chamber is in a vacuum pressure state. At this time, the receiver-stopper system includes a rotation shaft 61, a rotation actuator 63, an elevation actuator 64 and support plates 62 for supporting corners of the substrate 52.
A process of manufacturing a liquid crystal display device using the substrate assembly device according to the prior art will be described with reference to FIG. 2, which is a cross sectional view of a bonding device for a liquid crystal display device according to the related art during a bonding process, and FIG. 3 is a perspective view of a substrate support system of a bonding device for a liquid crystal display device according to the related art.
First, a second substrate 52 is attached to the upper stage 21, and a first substrate 51 is attached to the lower stage 22. Then, the lower chamber unit 32, having the lower stage 22, is moved by the chamber transfer means 40 to a working position for dispensing sealant and dropping liquid crystal material, as shown in FIG. 1. After the sealant dispensing process and the liquid crystal material dropping process are completed on the first substrate 51, the lower chamber unit 32 is moved again by the chamber transfer means 40 toward another working position for bonding between the substrates, as shown in FIG. 2. Then, the upper and lower chamber units 31 and 32 are coupled together by the chamber transfer means 40 to enclose a space where the stages 21 and 22 are positioned, and the elevation actuator 64 and the rotation actuator 63 constituting the receiver-stopper system are actuated to place the support plates 62 under two corners of the second substrate, which is attached to the upper stage 31. From this position, adsorptive force fixing the second substrate 52 is released to drop the second substrate 52 onto each of the support plates 62 of the receiver-stopper means as shown in FIG. 3.
At this time, pressure in an interior of the processing chamber is reduced to produce a vacuum state by a vacuum system. When the interior of the processing chamber is evacuated, an electrostatic force is applied to the upper stage 31 to attach the second substrate 52 while the rotation actuator 63 and the elevation actuator 64 are actuated so that the support plates 62 and the rotation shaft 61 do not obstruct bonding of the substrates. In the vacuum state, the upper stage 21 is moved downward by the stage transfer means 50, and bonds the second substrate 52, which is attached to the upper stage 21, and the first substrate 51, which is fixedly settled on the lower stage, thereby completing manufacturing processes of an LCD device.
The bonding device according the related art includes a number of working elements, specifically, working elements that require a considerable degree of precision, such as the stages and the substrate support means within the processing chamber. Accordingly, it is necessary to maintain the working elements at a precise distance according to the size and configuration of the first and second substrates. Moreover, since the first and second substrates may be different in their overall size and configuration and the substrates may have different cell configurations, it is necessary to carry out a selective operation according to the size and configuration of each substrate.
Considering that overall size of substrates are gradually increasing, there is a need to prevent drooping of the substrate by supporting an inside of the substrate rather than by supporting the corners during bonding processes. Accordingly, the working position of each working element preferrably should be changed according to the size and configuration of each substrate. Moreover, it is necessary to prevent any damage in the cell area by the working elements supporting dummy areas rather than the cell area including the color filter or TFT arrays.
However, as overall size and configuration of the substrates changes, positions and overall size of the cell area on the substrate is altered. Thus, once the working element is reproducibly positioned for a substrate having a first type of configuration, the working element may need to be repositioned to a substrate having a second type of configuration different from the first configuration. The bonding devices according to the related art are disadvantageous since different configurations of substrates require changing the configuration of the working elements. Specifically, when bonding substrates have a configuration different from a previously processed set of substrates, the bonding device must be reconfigured to establish a new set of working ranges corresponding to the new bonded substrates. Accordingly, in order to perform the bonding process with a new configuration of substrates in the conventional bonding process the working range of the each working element must be reconfigured. Thus, a significant increase is production processing time is required.